The Development of a Quantified Risk Factor for the Presence of Dark and/or Medullated Fibres in Australian Merino Wool

This publication is reproduced with the permission of Australian Wool Innovation Ltd (AWI), the funder of the work described in the paper, and the Federation of Australian Wool Organisations (FAWO), the research provider.

Abstract

Contamination of the Australian Merino clip has traditionally been associated with dark fibres originating from urine-stain and isolated pigmentation found in the fleece.

Over the last two decades, non-specialist woolgrowers introduced to Australia meat breeds often called exoticsa to meet the preferences of the live sheep trade. These breeds are crossed with Merinos to increase the number of exotics and to produce fat lambs. Contamination has resulted from the transfer of dark and/or medullated fibres from exotic breeds to Merinos, usually at mating and later when rearing an exotic cross lamb. Recent claims based on medullated fibre contamination of fabric have led to industry concern that the high reputation of the Australian clip may be affected.

An objective Pre-Sale Test is preferred. A manual, non-certified test based on a core-sample is offered by the Australian Wool Testing Authority Ltd, but due to high labour costs, the test is expensive and uptake low. Research, funded by Australian Wool Innovation, is underway to provide a more automated system; however, any development is a few years from commercialisation.

To address this situation, the Federation of Australian Wool Organisations, with funding from Australian Wool Innovation, initiated a project aimed at the introduction of a voluntary vendor (woolgrower) declaration for the risk of dark and/or medullated fibre contamination. To oversee the project and ensure its industry focus, a Working Group comprising representatives of all industry sectors was formed.

The project was founded on previous research, primarily by CSIRO and South Australian Department of Agriculture, who identified the major factors contributing to dark fibre contamination of Merino wool. This work ultimately resulted in a prediction scheme for urine-stained and/or isolated pigmented fibre. This CSIRO Dark Fibre Risk Scheme, which was validated by processing trials, calculated the “Risk” that a particular sale lot would meet the requirements of the white/pastel trade.

This paper reports on the development of a Dark and Medullated Fibre Risk (DMFR). The scheme is primarily based CSIRO’s Dark Fibre Risk Tree with additional information included on the contamination risk posed by contact with exotic breeds. The results of validation trials, conducted to provide a basis for any refinement to the scheme and to provide a sampling regime for possible future random testing, are presented.

It is proposed that the DMFR be a scale from 1 to 5, with Risk Levels 1 and 2 most suitable for sensitive end-uses. The objective information required for the calculation of the DMFR for Merinos includes wool types and description, sex, age, crutching, crutch/shear interval and mated to, reared or run with exotic sheep (or their crosses). The information would be collected on the Classer’s Specification or separate declaration form and the DMFR calculated at a central computer prior to reporting on test certificates and in auction catalogues.

With International Wool Textile Organisation and Australian Wool Exchange endorsement, this “Risk” will be reported on Test Certificates and in sale catalogues. The declaration will provide white wool producers with the opportunity to identify their product as such; while buyers/processors will have objective information on the potential risk of contamination.

Citation

"The Development of a Quantified Risk Factor for the Presence of Dark and/or Medullated Fibres in Australian Merino Wool", K.A. Hansford and Australian Wool Industry Working Group, Report RWG07, Raw Wool Group, IWTO Dubrovnik Meeting, November 2003.